JPS58208332A - Expandable thermoplastic polymer particle having good moldability - Google Patents

Abstract

PURPOSE:To provide expandable thermoplastic polymer particles having good moldability, by pelletizing an emulsion-polymerized thermoplastic polymer by extrusion to form particles, and impregnating the resultant particulate pellet with a blowing agent in an aq. suspension system. CONSTITUTION:A thermoplastic polymer such as polystyrene polymer is produced by emulsion polymn. and pellitized by extrusion to form particles. The pellet particles are impregnated with a blowing agent in an aq. medium to obtain expandable thermoplastic polymer particles having a water content of 1wt% or lower, pref. 0.7wt% or lower immediately after the production. In this way, the titled particles having good expandability and moldability can be obtd. Pref. the impregnation of the particles with the blowing agent in an aq. medium is carried out in the presence of a dispersant such as calcium tertiary phosphate to prevent pellets from being bonded to one another. When used together with an anionic surfactant, the effect is further enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to expandable synthetic resin particles having good moldability, and in particular, the present invention relates to expandable synthetic resin particles having good moldability. This shows a composition that improves the moldability of foamable synthetic resin particles obtained by impregnating a foaming agent in an aqueous suspension system.

As expandable synthetic resin particles, expandable styrene resin particles produced by suspension polymerization are generally known. Although this method is efficient because polymerization and blowing agent impregnation can be carried out continuously, the size distribution of the resulting suspended particles is smaller than the desired particle size range, which is often undesirable. Particles also have the disadvantage of being manufactured together. Furthermore, in suspension polymerization, α-
Polymerization of α-alkylstyrene such as methylstyrene and copolymerization with styrene cannot be carried out because the copolymerization reactivity of α-alkylene styrene is particularly low in a suspension polymerization system. Improvements in this respect were achieved by using emulsion polymerization. That is, polymerization is usually carried out by emulsion polymerization. 1) Coagulate the polymer latex, heat treat it, and dry it to form a polymer powder? () to be. The powder is made into pellets of only 940 pellets using an extruder.

The diameter of the obtained pellet is determined by the diameter of the die of the extruder and the cut strip f) of the cutter.The resulting synthetic resin pellet is again impregnated with a foaming agent in an aqueous medium to obtain foamable synthetic resin particles. However, the expandable synthetic resin particles produced by emulsion polymerization, pelletizing, and impregnation with a blowing agent deteriorate significantly in terms of expandability and moldability as the resin is left to stand, and cannot be put to practical use in a relatively short period of time. ? I was in a state where I had no jS.

In view of this, the present inventors conducted extensive research and found that the cause of this problem is that when the pellet is impregnated with a foaming agent in an aqueous medium, water, which is a suspending medium, enters the pellet together with the foaming agent.
In addition, we have discovered that the impregnated moisture dissipates when the foaming grains are left in the human SC (A11) (attributable to this), and we have completed the present invention. That is, the inside of the foaming grains containing an easily volatile foaming agent immediately after manufacture. When using expandable thermoplastic polymer particles having a moisture content of 1% by weight or less, particularly preferably 0.7% by weight or less, they have found that Example 11 provides good foamability and moldability.

In order to obtain foamable thermal aJGJj polymer particles with an internal moisture content of at least 1 part, for example, when impregnating a pellet with a foaming agent, a water-soluble inorganic salt of 100% is added together with a dispersant to the water suspension.
[Achieved with.

The polymerization polymer used in the emulsion polymerization in the present invention is not particularly limited, and examples include:
Afvn, α-methylstyrene, acrylonitrile, t
-butylstyrene, methyl methacrylate, di-1-butylreacrylate, 2-ethylhexyl acrylate, and ethyl acrylate'S.

Next, when the extruded pellets are impregnated with a foaming agent in an aqueous medium, a dispersant is used to prevent the pellets from sticking to each other. Any of these may be used and is not limited in the present invention. However, COD in water
Considering environmental regulations such as 4, inorganic dispersants are preferable. An example of an inorganic dispersion is tertiary calcium phosphate.

In this case, if a small amount of anionic surfactant is used in combination, the effect of the dispersant will be significant. The anionic surfactant used in combination has a pH of 0.0% relative to water. OLl 6~[], A1 weight Q% is sufficient. Examples of the anionic surfactant VL agent include, but are not particularly limited to, alkyl-I lebenzene sulfonate sodium, α-olef, inulfonate sodium, and rosin acid sorter ``lK''.

In this case, it does not matter in any way as long as a small amount of nonionic W surfactant is also used.

The blowing agent used in the present invention is a common easily volatile blowing agent. For example, propane, butahbentane, petroleum ether, triclochloromethane, cyclodifluoromethane, etc., these may be used alone or in combination. It is used as In addition, in order to increase the foamability of the foamable synthetic resin particles obtained during or before impregnation with a blowing agent, bath agents such as toluene, ethylbenzene, and methylene chloride may be soaked in the pellet. does not detract from the present invention in any way.

Examples of the present invention are described below.

Example 1 (1) Manufacture of polymer 41 of the following materials were charged into a reactor equipped with a stirrer.

Water 25 [1 part (+1 part, same as above) Sodium bourate 3 parts Sodium formaldehyde 1-sulfoxylate [1,4
ethylenecyaminetet) nizothorium chloride o,
01 parts Ferrous sulfate 110025 parts After deoxidizing, filtering in a nitrogen stream, heating and stirring at 0'C, Table 1
The monomer shown in Figure 2 was continuously polymerized by dropwise addition. After finishing dropping,
After further stirring at 60'C, polymerization was completed. After coagulating the produced polymer with calcium chloride, it was washed with water, filtered through 11 filtration, dried, and made into pellets. The obtained pellet had a diameter of about 1B.

Table 1 (2) Manufacturing of expandable synthetic resin particles The following substances (1) were placed in an autoclave equipped with a stirrer.

Water 1 (
]O part bet
1 old] part 6 calcium phosphate
05 parts Sodium α-olefin sulfonate o 02513 parts Water-bathable inorganic salts As shown in Table 2 Toluene
After 10 parts and nitrogen substitution, 90'
After heating and stirring for 2 hours in C), 9 parts of butane was press-fitted and 1
After raising the temperature to 10'C and maintaining it for 6 hours, it was cooled to 40'C, dehydrated, and dried to obtain expandable synthetic resin particles.

The internal moisture content of the resulting expandable synthetic resin particles A-1 to Δ-6 was measured after the day of production and one week after production. The results are shown in Table 6.

Table 6 Moisture is weight percent relative to resin.

Next, the obtained resins A-1 to A-6 were foamed with water vapor, and all showed good foaming properties.

Further, each of the resins A-1 to A-6 was subjected to ff-1iii foaming to a volume of +41 times, and after being left for 24 hours, molding was performed using a Toyo Kikai Gokku Shaso Burlstar 90 molding machine.

The mold used was 300 x 2 [] + J x 21 m.
This is a mold for molding a single plate of m. The surface condition of the molded object,
Good molding with excellent internal fusion properties (+).

Comparative Example Expandable synthetic resin particles -rU-1 to Ll-4 were obtained in the same manner as in the Example except that the inorganic salt was changed to rη shown in Table 4.

Table 4 Resin obtained [immediately after production of 3-1 to B-4 and 1 after production
Table 5 shows the results of measuring internal moisture for weeks [] r1';
I, ta.

Table 5 The water content is 111% based on the resin.

fl, ) Radar Resin I''-1 to 14-/l was foamed with water vapor, but the foaming could not be carried out sufficiently, and some grains were seen here and there that shrunk and became stale. Furthermore, resin B -1 to 11-
4 was pre-foamed to a magnification of [] times for 1 hour, and after being left for 24 hours, it was molded in the same manner as in Example (p).

The molded product obtained by molding was completely inferior in quality, with large gaps and no internal melting. .

[So, -1] As is clear from the difference between the Example and the Comparative Example, is there a foam with excellent foamability and moldability using the resin particles shown in the present invention? 1) Become.

Special + J'l Applicant Kanebuchi Chemical - F' Industry Co., Ltd. 1.1 Attorney - 4 Sada Asano -

Claims (1)

[Claims] 1. Thermoplastic polymer particles containing an easily volatile blowing agent,
Expandable thermal + iJ clear municipal particles, characterized in that the internal moisture immediately after production is 1% or more. 2. Expandable thermoplastic according to Patent No. 1:1"1, wherein the thermoplastic IF composite particles are produced by extrusion pelletization of the thermoplastic polymer powder obtained by emulsion polymerization (1). Polymer particles. 3 Thermal iJ plastic polymer particles A are polystyrene-based +1'1.
Expandable thermoplastic W1 polymer particles according to claim 1 or 2, which are coalesced particles; 0
■Plastic polymerization I4. Tag °f child.